There has been an increasing demand for improvements in the fuel consumption performance of pneumatic tires for the purpose of global environmental impact reduction in recent years. A known method of improving fuel consumption performance is to reduce the tire rolling resistance—that is, to reduce the heat build-up of the rubber composition that is used. With the objective of further reducing heat build-up while containing a butadiene rubber with a high cis structure, the present applicant has previously proposed a rubber composition containing a silica in an amount of from 10 to 120 parts by weight per 100 parts by weight of a diene-based rubber containing from 5 to 100 wt. % of a modified butadiene rubber, wherein the modified rubber is prepared by modifying a butadiene rubber having a cis content of not less than 90% with a nitrone compound having a nitrogen-containing heterocycle in the molecule (Patent Document 1).